Material-specific lateralization of prefrontal activation during episodic encoding and retrieval

Although numerous neuroimaging studies have examined the functional neuroanatomy supporting episodic memory for verbal material, there have been few investigations of non-verbal episodic encoding and retrieval. We used fMRI to directly compare prefrontal activation elicited by verbal and non-verbal material during encoding and during retrieval. Regardless of the mnemonic operation (encoding/retrieval), inferior prefrontal activation lateralized based on material type. Verbal encoding and retrieval resulted in greater left inferior prefrontal activation, whereas non-verbal encoding and retrieval resulted in greater right inferior prefrontal activation. The similarity between inferior prefrontal activity during encoding and during retrieval indicates that these mnemonic operations depend on shared processes mediated by inferior prefrontal regions.     

What is the mechanism for fluency in successive recognition?

There are a number of reasons to believe that processing fluency may affect successive recognition judgements, but evidence about the mechanism for these effects is currently lacking. This study used a successive task design to examine whether subjective ease might underlie effects of fluency on recognition. At study subjects performed lexical decisions; in a subsequent test with studied and new items, subjects performed lexical decisions followed immediately by recognition or ease judgments. In a previous study we used that process dissociation procedure to show that recognition in a similar task was largely based upon fluency. In the present study, successive recognition judgments interfered with lexical decision performance to a greater degree than did ease judgments, suggesting that the recognition judgment was not automatic and involved processes additional to the judgment of ease. The data suggest that the fluency involved in successive recognition is more complex than a subjective judgment of ease of processing. One possible mechanism for fluency in recognition may be based upon reductions in the orientation of attention that accompany item repetition.     

Striatal activation during acquisition of a cognitive skill.

The striatum is thought to play an essential role in the acquisition of a wide range of motor, perceptual, and cognitive skills, but neuroimaging has not yet demonstrated striatal activation during nonmotor skill learning. Functional magnetic resonance imaging was performed while participants learned probabilistic classification, a cognitive task known to rely on procedural memory early in learning and declarative memory later in learning. Multiple brain regions were active during probabilistic classification compared with a perceptual-motor control task, including bilateral frontal cortices, occipital cortex, and the right caudate nucleus in the striatum. The left hippocampus was less active bilaterally during probabilistic classification than during the control task, and the time course of this hippocampal deactivation paralleled the expected involvement of medial temporal structures based on behavioral studies of amnesic patients. Findings provide initial evidence for the role of frontostriatal systems in normal cognitive skill learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Images of medial temporal lobe functions in human learning and memory

Investigations of the neural basis of mammalian memory have focused more often on the medial temporal lobe (MTL) than on any other brain region. In humans, the amnesic syndrome revealed the essential importance of the multiple structures located in the MTL system for declarative memory (the remembrance of events and facts). Other neural systems mediate procedural forms of memory, including delay eyeblink conditioning, which depends on the cerebellum, and cognitive skill learning, which depends on the striatum. We review three functional imaging studies that reveal different patterns of MTL activation associated with declarative and procedural memory tasks. One study shows separate MTL activations during the encoding or retrieval of declarative memories. A second study shows MTL activation that occurs in parallel with cerebellum-dependent delay eyeblink conditioning, but does not appear to influence that form of procedural memory. A third study reveals suppression of the MTL during striatum-dependent cognitive skill learning. These studies provide images of MTL activations that are correlated with, independent from, or antagonistic to memory performance.     

"Selective corticostriatal dysfunction in schizophrenia: Examination of motor and cognitive skill learning": Correction to Foerde et al. (2008).

Reports an error in "Selective corticostriatal dysfunction in schizophrenia: Examination of motor and cognitive skill learning" by Karin Foerde, Russell A. Poldrack, Barbara J. Knowlton, Fred W. Sabb, Susan Y. Bookheimer, Robert M. Bilder, Don Guthrie, Eric Granholm, Keith H. Nuechterlein, Stephen R. Marder and Robert F. Asarnow (Neuropsychology, 2008[Jan], Vol 22[1], 100-109). The DOI for the supplemental materials was printed incorrectly. The correct DOI is as follows: http://dx.doi.org/10.1037/0894-4105.22.1.100.supp. (The following abstract of the original article appeared in record 2008-00382-011.) It has been suggested that patients with schizophrenia have corticostriatal circuit dysfunction (Carlsson & Carlsson, 1990). Skill learning is thought to rely on corticostriatal circuitry and different types of skill learning may be related to separable corticostriatal loops (Grafton, Hazeltine, & Ivry, 1995; Poldrack, Prabhakaran, Seger, & Gabrieli, 1999). The authors examined motor (Serial Reaction Time task, SRT) and cognitive (Probabilistic Classification task, PCT) skill learning in patients with schizophrenia and normal controls. Development of automaticity was examined, using a dual task paradigm, across three training sessions. Patients with schizophrenia were impaired at learning on the PCT compared to controls. Performance gains of controls occurred within the first session, whereas patients only improved gradually and never reached the performance level of controls. In contrast, patients were not impaired at learning on the SRT relative to controls, suggesting that patients with schizophrenia may have dysfunction in a specific corticostriatal subcircuit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in prefrontal cortical brain activity during fMRI of auditory verbal working memory.

Functional imaging studies of sex effects in working memory (WMEM) are few, despite significant normal sex differences in brain regions implicated in WMEM. This functional MRI (fMRI) study tested for sex effects in an auditory verbal WMEM task in prefrontal, parietal, cingulate, and insula regions. Fourteen healthy, right-handed community subjects were comparable between the sexes, including on WMEM performance. Per statistical parametric mapping, women exhibited greater signal intensity changes in middle, inferior, and orbital prefrontal cortices than men (corrected for multiple comparisons). A test of mixed-sex groups, comparable on performance, showed no significant differences in the hypothesized regions, providing evidence for discriminant validity for significant sex differences. The findings suggest that combining men and women in fMRI studies of cognition may obscure or bias results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationship between skill learning and repetition priming: experimental and computational analyses

Skill learning and repetition priming are considered by some to be supported by separate memory systems. The authors examined the relationship between skill learning and priming in 3 experiments using a digit entering task, in which participants were presented with unique and repeated 5-digit strings with controlled sequential structure. Both skill learning and priming were observed across a wide range of skill levels. Performance reflected the effects of learning at 3 different levels of stimulus structure, calling into question a binary dichotomy between item-specific priming and general skill learning. Two computational models were developed which demonstrated that previous dissociations between skill learning and priming can occur within a single memory system. The experimental and computational results are interpreted as suggesting that skill learning and priming should be viewed as 2 aspects of a single incremental learning mechanism.     

Selective corticostriatal dysfunction in schizophrenia: Examination of motor and cognitive skill learning.

[Correction Notice: An erratum for this article was reported in Vol 22(3) of Neuropsychology (see record 2008-05020-015). Table 1 on page 102 should have included the BPRS Depression-Anxiety subscale score 9.00 (3.99) under the column heading Schiz pts. Table displays means with standard deviations in parentheses.] [Correction Notice: An erratum for this article was reported in Vol 22(2) of Neuropsychology (see record 2008-02526-002). The DOI for the supplemental materials was printed incorrectly. The correct DOI is as follows: http://dx.doi.org/10.1037/0894-4105.22.1.100.supp.] It has been suggested that patients with schizophrenia have corticostriatal circuit dysfunction (Carlsson & Carlsson, 1990). Skill learning is thought to rely on corticostriatal circuitry and different types of skill learning may be related to separable corticostriatal loops (Grafton, Hazeltine, & Ivry, 1995; Poldrack, Prabhakaran, Seger, & Gabrieli, 1999). The authors examined motor (Serial Reaction Time task, SRT) and cognitive (Probabilistic Classification task, PCT) skill learning in patients with schizophrenia and normal controls. Development of automaticity was examined, using a dual task paradigm, across three training sessions. Patients with schizophrenia were impaired at learning on the PCT compared to controls. Performance gains of controls occurred within the first session, whereas patients only improved gradually and never reached the performance level of controls. In contrast, patients were not impaired at learning on the SRT relative to controls, suggesting that patients with schizophrenia may have dysfunction in a specific corticostriatal subcircuit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)